RFR: 8300732: Whitebox functions for Metaspace test should use byte size [v2]

[Sonia Zaldana Calles]

> Hi all, 
> 
> This PR addresses [8300732](https://bugs.openjdk.org/browse/JDK-8300732) switching Whitebox Metaspace test functions to use bytes as opposed to words. 
> 
> Testing: 
> - [x] `test/hotspot/jtreg/runtime/Metaspace` tests pass. 
> 
> Thanks, 
> Sonia

Sonia Zaldana Calles has updated the pull request incrementally with two additional commits since the last revision:

 - Hard coding values and adding Unit class
 - whitebox changes based on feedback. Using is_aligned and asserts

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/20039/files
  - new: https://git.openjdk.org/jdk/pull/20039/files/5dcc6c9e..7c0138ca

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20039&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20039&range=00-01

  Stats: 83 lines in 6 files changed: 42 ins; 19 del; 22 mod
  Patch: https://git.openjdk.org/jdk/pull/20039.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20039/head:pull/20039

PR: https://git.openjdk.org/jdk/pull/20039